Electrical stimulation of tissue for therapeutic and diagnostic purposes

ABSTRACT

Electrobiological stimulation is carried out transcranially by applying high frequency squarewave bursts exhibiting no d.c. term across the cranial region. Such stimulation is commenced employing ramp generators and positive and negative voltage converters which evolve the requisite baseform and burst frequencies having a voltage waveform which is square in nature. Both voltage and current are sensed and subjected to comparator logic in conjunction with predetermined thresholds and windows. Overcurrent detection and overvoltage detection is provided in hard wired fashion to assure rapid shutdown response. D.C offset detection is provided along with waveform balance tests to further assure the safety of the system. Diagnostic procedures as well as therapeutic procedures may be carried out with a system version which provides for the application of a stimulus in conjunction with safety monitoring and controller based development of stimulating waveforms, all of which exhibits no d.c. term. Feed point voltage waveforms and current waveforms are mathematically processed and compared for diagnostic analysis.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a division of prior application Ser. No.10/272,094,filed Oct. 16, 2002, which is a continuation-in-part of priorapplication Ser. No. 09/661,068, filed Sep. 13, 2000, the disclosures ofwhich are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

Alternative medicine approaches to the treatment of a variety ofphysical and mental conditions have been the subject of substantialinvestigation and interest. See: Journal of the American MedicalAssociation (1998), 280 (18). Nontraditional techniques in themanagement of pain have ranged from classic acupuncture to theelectrical stimulation of tissue. In the latter regard, the efficacy ofelectrical stimulation from skin surface attached electrodes have beenthe subject of a substantial amount of investigation. Referred togenerally as transcutaneous electrical nerve stimulation (TENS),typically a relatively low level of current, for example, in themilliamp range which is manifested as a squarewave is introduced to someselect region of the peripheral nervous system for a prescribedtreatment interval. The frequency of this squarewave signal isrelatively low, ranging generally from a few Hertz to about 100 Hertzand patient response to the application of such low frequency currentsat the skin has been described as an unpleasant experience.

Somewhat recently, a combination of electrical stimulation andacupuncture has evolved. This technique differs from traditionalacupuncture in that the needle itself is not the focus of treatment,instead, it serves as a conductor of electricity. One approach withelectroacupuncture has been described as percutaneous electrical nervestimulation (PENS). This PENS therapy utilizes acupuncture-like needleprobes positioned in the soft tissue to stimulate peripheral sensorynerves at the dermatomal levels.

In the 1970s, Limoge, working in France, evolved an electroanesthesiaelectroanalgesia approach involving a different form of stimulationsometimes referred to as “Limoge currents” wherein, for example, a pulsecycle comprising pulses consisting of a positive wave for 2 μS isfollowed by a negative wave of 4 μS. The group has a period duration of6 μS corresponding to 166 kHz. These groups have been referred to asbi-phasic balanced currents. They are gated on for four millisecondsfollowed by an off period of six milliseconds. The total cycle periodthus is ten milliseconds corresponding to a 100 Hz gating cycle or burstfrequency.

The integrals of the positive high frequency pulses and the negativehigh frequency pulses are maintained in balance. This results in a zeronet applied current and eliminates or substantially abates a potentialfor electrophoresis. The current intensity generally will be from about220 mA to about 250 mA peak to peak. In general, application of thecurrent is by transcranial electrical stimulation (TCES) which isapplied to the head through a frontal electrode and two posteriorelectrodes at the level of the mastoid bones. TCES treatment evidencesno apparent side effects and has been used with very positive results inabdominal, urological gynecolgical and orthopedic surgery andtraumatology and in addiction withdrawal therapy. TCES has been shown toenhance the potency of conventional pharmaceuticals during surgery andto evoke a reduction in the need for opiate analgesic duringneuroleptanalgesia. Mathematical analysis of the Limoge currentsindicates that the use of high frequency currents allow deep penetrationof the electric field into the brain. It has been thought that thedielectric properties of biological tissue enables, in situ, the highfrequency current combination with low frequency currents is responsiblefor the analgesic potentiaton. See the following publications:

-   -   Limoge, A., An introduction to electroanaesthsia. In: R. M.        Johnson (Ed.), University Park Press, Baltimore, Md., 1975, pp.        1-121.    -   Limoge, A., Louville, Y., Barritault, L., Cazalaa, J. B. and        Atinault, A., Electrical anesthesia. In: J. Spierdijk, S. A.        Feldman, H. Mattie and T. H. Stanley (Eds.), Developments in        Drug Used in Anesthesia, Leiden University Press, Leiden, 1981,        pp. 121-134.    -   Limoge, A. and Boisgontier, M. T., Characteristic of electric        currents used in human anesthesiology. In: B. Rybak (Ed.),        Advanced Technology, Sijthoff and Noordhoff, German-town, 1979,        pp. 437-446.    -   Champagne, Papiernak, Thierry, and Noviant, Transcutaneous        Cranial Electrical Stimulation by Limoge Currents During Labor,        Ann. Fr. Anesth. Reanim., Masson Paris, 1984.    -   Stanley, T. H., Cazalaa, J. A., Atinault, A., Coeytaux, R.,        Limoge, A. and Louville, Y., Transcutaneous cranial electrical        stimulation decreases narcotic requirements during neuroleptic        anesthesia and operation in man, Anest. Analg., 61 (1982)        863-866.    -   Stanley, T. H., Cazalaa, J. A., Limoge, A. and Louville, Y.,        Transcutaneous cranial electrical stimulation increases the        potency of nitrous oxide in humans, Anesthesiology, 57 (1982)        293-297.    -   Ellison, F., Ellison, W., Daulouede, J. P., Daubech, F. E.,        Pautrizel, B., Bourgeois, M. and Tignol, J., Opiate withdrawal        and electrostimulation double blind experiments, Encephale,        13 (1987) 225-229.

In support of an expanded utilization of the Limoge currents in thecontrol and management of pain and a variety of medical conditions,investigators and practitioners now find need for improved generationequipment with heightened capacities for investigation of variations ofthe Limoge current signatures or characteristics and for utilization ofthese variations and their effect for diagnostic applications totreatment as well as therapeutic purposes.

BRIEF SUMMARY OF THE INVENTION

The present invention is addressed to the subject of electrobiologicalstimulation. It particularly is directed to the introduction of systems,devices and methods which not only support current therapeutictechniques of electrostimulation considered effective, but also provideinvestigators, including research clinicians, with a support systempermitting enhanced research endeavors.

The system has been evolved with a recognition that an electricalwaveform can be applied to a load, here tissue, exhibiting variable andunknown electrical impedance characteristics in a manner wherein thoseelectrical characteristics can be analyzed. Those electricalcharacteristics will correspond with the tissue characteristics of thematerial constituting such load. For the present investigatory system,that load may be the animal head. Expanding upon the electrodestimulation developed by Limoge (TCES) the present system exhibitsenhanced procedures and efficiencies for carrying out now establishedtherapeutic protocols. As an adjunct to these features, the system andtechnique provide apparatus and method with capabilities for supportingboth patient stimulation as well as diagnosis and clinical research inelectrobiological stimulation technologies. In the latter regard, theinstant approach recognizes that rectangular waves comprising highfrequency harmonics of base frequency signals with positive-going andnegative-going features are combined to exhibit no d.c. term. Ingeneral, the ultimately derived waveforms are assembled by gating at aburst frequency. However, when high frequency is applied to a biologicalload such as a human head, a resultant current waveform, when comparedto the corresponding applied or feed point voltage waveform, willexhibit aberrations representing, for example, impedance characteristicsof the cranial region through which current passes. Digitization andanalysis of these two waveforms evolves valuable diagnostic data. Suchanalysis will include Fourier transform definition of both waveforms inconjunction with mathematical analyses thereof which manipulate datarepresenting their differences. Laplace-mathematical operators alsoprovide substantial analysis of the impedance characteristics throughoutthe region coursed by one or more channels of current flow. As isapparent, as such analysis is applied to an expanding patientpopulation, an important database can be evolved with a library ofaccessible mathematical parameters, biological parameters and symptomparameters to evoke expanding diagnostic possibilities and accuracies.Thus, the apparatus, system and method of the invention is directed toproviding practitioners and researchers an improved therapeuticcapability coupled with a unique diagnostic opportunity.

In one embodiment, apparatus is provided for applying current fortherapeutic purpose which incorporates a control assembly. That controlassembly performs in conjunction with positive and negative voltageconverters operating in two channels, as well as a network of voltageand current monitors. The control assembly determines impedance valuesfor each channel and carries out comparison procedures to evaluate notonly that impedance, but peak values of voltage and current, overvoltageand overcurrent conditions, and channel balance conditions. Where thoseoperational parameters are beyond specified limits, the apparatus isautomatically shutdown. Detection of any d.c. term greater than somelimit and resultant shutdown also is made for the safety of the patient.

In another embodiment, a controller is provided which affords thepractitioner substantial versatility and waveshape structuring, afeature particularly valuable for carrying out a variety ofelectrobiologic diagnostic procedures. This controller mathematicallyprocesses monitored voltage and current at the feedpoint electrodes toderive a broad variety of electrically defined biological factors.Memory is employed not only to retain such data but also to provide alibrary of similar data derived from patient populations.

A particular feature available with the controller and associated memoryresides in the provision of a gatekeeping form of control over thecontroller in combination with portable data collection throughutilization of a patient data card. The card is a microprocessor driven“smart card” carrying archival memory, treatment protocol, calendar andtime information. In use, a physician prescribes a protocol for date,time interval of treatment, and any waveshape data which are written tothe card. The treatment apparatus with controller then can only beenabled by the patient by card insertion into a controller read/writecomponent. At the end of each treatment, collected data is downloaded tothe card for future physician reference and medical record development.

As another feature, the invention provides a method for applying anelectrical stimulus transcranially to an animal with surface regionslocated adjacent a volume of tissular material, comprising the steps of:

-   -   (a) providing first and second electrode assemblies of        respective first and second polarities;    -   (b) providing electrical generation apparatus electrically        coupled with the first and second electrode assemblies,        responsive to a generator input to provide an excitation output,        across the first and second electrode assemblies at frequencies        and with waveshapes exhibiting given electrical characteristics;    -   (c) providing a current sensor assembly responsive to the        electrical excitation outputs for providing a monitored current        value output;    -   (d) providing a voltage sensor assembly responsive to the        electrical excitation outputs for providing a monitored voltage        value output;    -   (e) providing a controller having a memory and a display and        controllable to derive a generator input for producing the        excitation output exhibiting predetermined frequencies and        waveforms;    -   (f) electrically coupling the first electrode assembly to the        first surface region;    -   (g) electrically coupling the second electrode assembly to a        second surface region spaced from the first surface region;    -   (h) controlling the controller to derive a generator input to        produce an excitation output across the tissular volume for a        predetermined application interval, such excitation output        having electrical characteristics defining the waveform with        positive-going and negative-going waveform components combined        to exhibit substantially no d.c. term and occurring at a base        frequency value and at a burst repetition frequency value less        than the base frequency value;    -   (i) controlling the controller to record in the memory, the        monitored voltage output as voltage data corresponding with the        electrical characteristic; and    -   (j) controlling the controller to record in the memory the        monitored current output in correspondence with the monitored        voltage output as current data corresponding with the electrical        characteristics and influenced by the impedance characteristics        extant at the volume of tissular material.

Other objects of the invention will, in part, be obvious and will, inpart, appear hereinafter.

The invention, accordingly, comprises the system and method possessingthe construction, combination of elements, arrangement of parts andsteps which are exemplified in the following detailed description.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description taken inconnection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic representation of voltage and current waveshapesutilized with the system of the invention;

FIG. 2 is a schematic representation of the gated duration of thewaveforms of FIG. 1;

FIG. 3A is a schematic representation of a human head with theapplication of two electrodes at the cranial region, while FIG. 3B is afrontal view of the head of FIG. 3A showing the positioning of threeelectrodes;

FIG. 4 is an electrical block diagram of one embodiment of apparatusaccording to the invention;

FIG. 4A is a graphical representation of threshold ranges utilized bythe circuit of FIG. 4 for determining impedance characteristics for eachchannel;

FIGS. 5A and 5B combine as labeled thereon to show a block schematicsystems diagrams for another embodiment of the invention;

FIGS. 6A-6G combine to provide a flowchart describing the operation ofthe system of FIGS. 5A and 5B;

FIGS. 7 is a flowchart describing a general diagnostic procedure for thesystem of FIGS. 5A and 5B;

FIG. 8 is a block diagrammatic representation for a sweep frequency formof diagnostic procedure utilized by the system of FIGS. 5A and 5B;

FIG. 9 is a flowchart showing a run monitor subroutine employed with theprogram represented at FIGS. 6A-6G;

FIG. 10 is a flowchart describing a wavecheck subroutine employed by theprogram of FIGS. 6A-6G;

FIG. 11 is a block schematic diagram illustrating components andfunctions of a system for carrying out one version of diagnosis andtherapy utilized by the system of the invention; and

FIG. 12 is a block schematic diagram representing the functions andcomponents of a diagnostic implementation of the invention.

DETAILED DESCRIPTION OF THE INVENTION

In the discourse to follow, an initial apparatus is described whichfunctions to generate a Limoge signal in terms of a high frequency (167kHz) where a positive-going waveshape is produced for an interval of twomicroseconds, followed by a negative-going continuum of one half theabsolute value of the positive-going amplitude but for an interval offour microseconds. This high frequency signal thus carries no d.c. term.A zero d.c. term characteristic avoids iontophoresis or damaging saltbuildup in the tissue of the patient. This high frequency waveform isproduced for a burst interval of four ms ON followed by an OFF intervalof 6 ms. Such sequence is repeated at each ten ms interval. In theLimoge constructed devices heretofore in use, the operator of thegenerator system observes current values at an ammeter and graduallyelevates voltage by turning a dial to, in turn, evolve a current valuewhich increases until it reaches a desired current peak-to-peakamplitude which heretofore has been established as 140 milliamps perchannel. As that current value is observed, the operator ceases voltageelevation and the treatment is carried out for some prescribed interval,for example, three hours. Two channels are utilized for application ofthis current. To provide these two channels, two input electrodes areutilized which are applied to the skin surface of the patient at themastoid region in back of the ear and a return electrode also is appliedto the patient at the center of the forehead. In general, a capacitorhaving a coupling function is utilized in this Limoge system to assurethat any d.c. term is avoided. With the initial embodiment shown, awaveform at the noted high frequency is generated with a positive-goingamplitude which is twice that of an immediately subsequently occurringnegative component, the latter of which has a duration which is twicethat of the positive-going component and at an amplitude of one half ofthe positive going component.

Looking to FIG. 1, the high frequency aspect of the applied waveformemployed with the present invention is represented generally at 10. Thesquarewave involved is shown at 12, partially in dashed line fashion.This squarewave persists for an interval of two microseconds, whereuponit is continued with the squarewave represented partially in dashed linefashion at 14 as a negative-going component which persists for fourmicroseconds and has an amplitude equal to one half that of thepositive-going component 12. Where the current passing from a feedelectrode assembly to a return is observed, it will exhibit a rounded orattenuated characteristic. For example, the positive-going component 12will be rounded as shown at the curve region 16 and the negative goingcomponent 14 will be rounded as shown by the solid line curve portion18. With the present approach to this waveshape phenomena, it has beendetermined that the differential or difference between this roundedcurve form shown in solid line fashion at 16 and 18 and the appliedsquarewave will represent inter alia, information or data which willcorrespond to electrical parameters such as impedance exhibited by thetissue, for example, cerebral, through which the current passes.

FIG. 2 shows the burst characteristics of the signal transmitted throughthe electrodes. In this regard, the squarewave is produced at highfrequency for an interval of four milliseconds and turned off for asucceeding six milliseconds whereupon it again is generated. Thisprovides for a burst or gated pulse commencing each ten milliseconds.The amplitude of this signal generally ranges between 30-50 volts.

Application assemblies or electrodes which are utilized in applying thenoted current may take a variety of configurations, for example,electrodes similar to those used with conventional EKG devices have beensuggested. However, surface electrodes retained in skin contactingposition by a harness-like structure have been found to be beneficial.In general, the devices are utilized in conjunction with an electricalcoupling enhancing ointment or the like. In FIGS. 3A and 3B a returnelectrode is shown at 20 attached to a skin region of the patient 22located at the forehead. This positioning is between the eyes as seen inFIG. 3B. Two, channel defining input electrodes are positioned againstthe opposed sternocleido mastoid, i.e., just below the ear. Thesechannel designated electrodes are represented at 24 and 26 in thefigures. Leads 28-30 are shown extending from respective electrodes 20,24 and 26. The leads extend to terminals on the generating apparatus. Asis apparent, current passing through the electrode pair 24-20 andelectrode pair 26-20 will traverse cranial tissue including the brain.That tissue will exhibit, for example, electrical parameters whichinclude the impedance of that region of current passage.

Now turning to FIG. 4, an initial embodiment of improved generatingapparatus for utilization with the electrodes described in connectionwith FIGS. 3A and 3B is presented. For convenience and safety ofapplication, this equipment is battery powered. In the figure, a 12 voltbattery pack is represented at block 30. This battery power supplyprovides an internal power supply as represented at line 32 and block 34and, as represented at lines 36 and 38, provides a power input to pairedpositive and negative voltage converters. These converters establish twochannels of excitation output leading to electrodes as described aboveat 24 and 26. Line 36 provides power input to a positive voltageconverter represented at block 40, as well as through line 42 to anegative voltage converter represented at block 44. In similar fashion,line 38 extends from line 36 to the second channel voltage converters.In this regard, lines 38 and 48 are seen directed to the input of apositive voltage converter represented at block 46, while line 38extends to the input of a negative voltage converter represented atblock 50. These voltage converters may be implemented, for example, asswitch-mode d. c.-d. c. converters of type ADP1108 marketed by AnalogDevices, Inc., of Norwood, Mass. At the commencement of a procedure, thed.c. outputs of these converters, as represented at lines 52-55 aregradually increased from 0 voltage to a predetermined therapeutic level,for example, at a ramp rate which is relatively slow, for example, 10volts per second. Ramp control into the converter pairs for each of thechannels is provided by a ramp generator. In this regard, the rampingcontrol over converters 40 and 44 is provided by a ramp generatorrepresented at block 58. Correspondingly, the ramp control of voltageconverters 46 and 50 is provided by a ramp generator 60. These controlinputs are represented, in the case of ramp generator 58, by lines 62and 64, while corresponding control inputs from ramp generator 60 arerepresented at lines 66 and 68. Ramp generators 58 and 60 may beimplemented for example, utilizing operational amplifiers of a typeLM741 marketed by National Semiconductor Corporation of Santa Clara,Calif. Enablement and starting of the ramp generator control is providedfrom a Timer/Shutdown logic function represented at block 70, suchcontrol with respect to ramp generator 58 being represented at line 72and corresponding control to ramp generator 60 being represented at line74. The Timer/Shutdown logic 70 may be implemented with programmablelogic devices, for example, a CMOS PAL device of type PLC18V8Z35marketed by Philips Semiconductor Corp of Sunnyvale, Calif.Timer/Shutdown logic 70 represents the logic component of a controlassembly represented generally at 76. In this regard, the logiccomponent 70 responds to user input or user controls as represented atblock 78 and line 80. Such control inputs from the user control 78 willinclude a start actuation function to derive a start input, as well as astop actuation to derive a stop input. The logic function 70additionally responds to clinician control inputs as represented atblock 82 and line 84. These clinician controls 82 are concealed suchthat the device can be used by the patient. However, such control inputswhich are not accessible by the patient will include the total dosagepermitted in terms of the times and duration of application of thetherapy, as well as the parameters of the waveform and frequency.Accordingly, the user controls at 78 are primarily an on and an offfunction to commence or terminate a given therapy.

Upon the voltage converters reaching their designated or target(threshold) voltage and current levels, the logic function 70 willprovide a timing output representing the time interval remaining in agiven therapy session. This visual indicia is represented at line 86 andblock 88. Additionally, the logic function 70 will provide an outputrepresenting an appropriate on-going therapeutic interval which may beprovided, for example as a green light emitting diode (LED).Additionally, where any electrode as at 20, 24 and 26 exhibits ananomaly such as being improperly positioned, a warning indicia will beprovided and, further, where a monitored condition is derived whichcalls for a stopping of a therapy, a red LED will be illuminated inconjunction with a system shutdown. This status display output from thelogic function 70 is represented at line 90 and block 92.

Returning to the voltage converter functions, the higher frequency, f1,waveform 10 as well as the lower frequency, f2, burst frequency andoutput timing intervals are generated in rectangular wave fashionutilizing one half H bridge drivers. In this regard, the first channel(A) d.c. positive voltage output at line 52 and the negative d.c.voltage output at 53 are seen directed to a bridge driver represented atblock 94. In similar fashion, the corresponding second channel (B)voltage converter outputs at lines 54 and 55 are directed to the inputsof an identical bridge driver represented at block 96. Drivers 94 and 96may be provided as incorporating half-bridge N-channel power MOSFETdrivers, for example, a type LT1160 marketed by Linear TechnologyCorporation of Milpitas, Calif. These devices 94 and 96 are under thecommon control of a waveform generator represented at block 98. Suchcontrol is represented at lines 100 and 102. In turn, the waveformgenerator 98 is under the control of the logic function 70 asrepresented at line 104. The generator function 98 may be implemented,for example, as a CMOS timer of type LMC555 marketed by NationalSemiconductor Corporation (supra).

It is from the waveform generator function 98 that the rectangular wavediscussed in connection with FIGS. 1 and 2 is developed by control overthe positive and negative inputs to the bridge drivers 94 and 96. At thecommencement of a given therapy, the peak-to-peak value of thiswaveshape as now developed respectively at lines 106 and 108 fromdrivers 94 and 96, will progressively increase in value until such timeas a peak target (threshold) current is reached. At that time, thewaveshape is under stabilization control in terms of current and voltagefor the duration of the therapeutic treatment. A current sensingfunction for the channel “A” output at line 110 is represented at block112. Operating in conventional manner, the sensor function 112 producesa voltage signal at line 114 having a value which is proportionate tothe instantaneous value of current at line 110. Sensor 112 may beimplemented with a type PE63587 current sense transformer marketed byPulse Corp of San Diego, Calif. The signal at line 114 is shown, interalia, being directed via line 116 to a peak current detector representedat block 118. Detector 118 may be implemented, for example, with a highspeed, BiFET operational amplifier marketed as a type AD711 by AnalogDevices, Inc., (supra). As the ramp threshold is reached, an output fromthe peak current detector 118 at line 120 functions to stabilize theramp generator 58 for this one channel, A.

The second channel, identified as output B, as derived in conjunctionwith bridge driver 96 and line 108, incorporates an identical currentsensor represented at block 122 and the excitation output is seen tocontinue as represented at line 124. Current sensor function 122provides a signal, corresponding with the current at line 124, alonglines 126 and 128 to a peak current detector function represented atblock 130. A signal output from peak current detector 130 is directed,as before, via lines 132 and 134 to the ramp generator 60, functioningto cause a stabilization of that ramp output upon reaching the value ofa ramp threshold signal or value.

Peak voltage detection is carried out for the first channel identifiedas output A by a peak voltage detector function represented at block136. In this regard, voltage is monitored from output line 110 asrepresented at lines 138 and 140 and, as before, the voltage detectorfunction may be implemented with a high speed, BiFET operationalamplifier of a type AD711 (supra).

The peak voltage detection function is repeated in conjunction with thesecond channel represented as output B. In this regard, the peak voltagedetection function is represented at block 142 for this second channel.Voltage monitoring is from output line 124, which is seen connected withlines 144 and 146 leading to the detection function 142. The output ofpeak voltage detector 142 is seen at line 148 to be extending to oneinput of a Range Comparators function represented at block 150. In thisregard, the peak current detector output at line 132, which also extendsto comparators function 150, provides a monitored current value output.Correspondingly, the peak voltage detector provides a monitored voltagevalue output. These outputs are specific to the second channelrepresented as output B. The comparators function 150 may beimplemented, for example, with high-speed comparators such as type LM119marketed by National Semiconductor Corporation (supra). Both during theramping procedure and following that procedure during therapy, when themonitored current value output at line 132 and the monitored voltageoutput at line 148 represents a load impedance not within apredetermined load impedance range, then an impedance fault signalspecific to the second channel represented at output B will be generatedby the comparators 150 and presented to the timer shutdown logic 70 asrepresented at line 152. The control assembly 76 then will respond tosuch an input to derive a stop input terminating the generation ofexcitation outputs at lines 110 and 124.

In similar fashion, the monitored current value output from peak currentdetector 118 at line 154 and the corresponding monitored voltage valueoutput from peak voltage detector 136 at line 156 are directed to aRange Comparators function represented at block 158. The comparatorsfunction 158 responds to a predetermined load impedance value andderives an impedance fault signal for the first channel represented asoutput A when the monitored voltage value output and the monitoredcurrent value output at respective lines 156 and 154 represent animpedance not within the predetermined load impedance range. A firstchannel designated impedance fault signal then is created at line 160which is directed to the timer/shutdown logic at block 70 to turn offthe apparatus. At such time that the currents are turned off, anappropriate fault indicia is provided at the status display 92.

An interesting aspect of the fault evaluation made by the rangecomparators resides in the impedance based nature of the fault. Forexample, the predetermined load impedance range or acceptable loadimpedance range which is employed by the range generators 150 and 158may be represented by a sequence of acceptable voltages and acceptablecurrents extending between zero value at the commencement of rampgeneration to maximum values which will be realized when the rampthreshold signal is generated stabilizing the outputs of the two drivers94 and 96. These voltage and current impedance characteristics can begraphically portrayed. Looking momentarily to FIG. 4A, for a givenchannel, channel current is plotted in relationship to channel voltage,a target or median relationship being represented by the solid line 170.A first or upper acceptable increasing range of voltage andcorresponding current values is represented by the dashed line 172.Correspondingly, a second range of increasing acceptable voltage andcorresponding current values is represented as a second lower range atdashed line 174. The ramp threshold values are represented as i_(max) atdashed line 176, while the corresponding threshold value for voltage isrepresented as V_(max) at dashed line 178 Because of the impedancecharacteristic at the feed electrodes fastened to the skin region of thepatient, for a given value of voltage, for example, that shown at V₁, anacceptable highest value of current is represented at i₁. However, forthat voltage value, V₁, if the current is less than the correspondingacceptable value current of the second or lower range 174, i.e., belowi₂, then an impedance fault signal is derived as an electrode faultsignal indicating to the practitioner that an electrode for the channelat hand is not properly installed. By contrast, the control assemblyderives the impedance fault signal as a low impedance fault signal,e.g., resembling a short circuit, when for any given value of voltage ofboth the first and second ranges at dashed lines 172 and 174, the valueof current is greater than the corresponding acceptable value of thecurrent of the higher or first range represented at dashed line 172. Forexample, if the current falls between locations V₁, and V₂, a currenthigher than i_(i) will evolve an impedance fault signal. These two typesof impedance fault signals are indicated to the practitioner at thestatus display 92.

Returning to FIG. 4, the apparatus of the invention additionally carriesout a test for waveform balance between the output at line 110 and theoutput at line 124. This inter-channel output test feature isrepresented at block 180 which, for the instance embodiment, comparesthe amplitudes of current of the first channel represented as output Aand the second channel represented as output B. In this regard note thatthe current sensor 112 output is directed via line 114 and the line 182to one input of the waveform balance network 180. The same form of inputfrom current sensor 122 is directed via lines 126 and 184 to theopposite input to the network 180. While any of a variety waveformcharacteristics may be employed for this interchannel waveform balanceevaluation, that shown is one wherein a peak value of current at onechannel is monitored and compared with a corresponding peak value ofcurrent at one channel is monitored and compared with a correspondingpeak value of current in the second channel. The peak current differencevalue then is compared to a predetermined peak current balance limitvalue. A balance fault signal is generated at line 186 when the peakcurrent balance value exceeds the predetermined peak current balancelimit value. That signal, in turn, causes the Timer/Shutdown logic 70 toterminate the outputs of the two channels and provide a correspondingfault message at the status display 92.

As indicated earlier herein, the high frequency components of thewaveform will exhibit positive and negative energy equivalence in orderto avoid any presence of a net d.c. waveform term. Avoidance of such aterm prevents salt buildup in tissue, an undesirable condition referredto as “iontophoresis”. Accordingly, the monitoring functions for theapparatus include a d.c. off-set Integrator/Detector for each of thechannels identified as having output A and output B. Concerning theformer, it may be observed that the signal from current sensor 112 ismonitored via lines 114 and 188 by an Integrator/Detector represented atblock 190. Accordingly, should the detector 190 identify a d.c. offset,a fault signal is transmitted to the Timer/Shutdown logic 70 to turn offcurrent in both channels as represented by arrow 192.

The second channel, identified as output B similarly is monitored for ad.c. offset. In this regard, a signal from current sensor 122 ispresented along lines 126 and 192 to a d.c. offset Integrator/Detectorrepresented at block 194. Upon detecting any d.c. offset, detector 194similarly provides a fault signal to the Timer/Shutdown logic 70 asrepresented by arrow 196. As before, this causes the apparatus to beturned off. When any such d.c. offset fault signal occurs, anappropriate message is provided at the status display 92

In the interest of patient safety, both of the channels of the apparatusare monitored by an over-current detector as represented at block 200and an over-voltage detector represented at block 202. In this regard,over-current detector 200 responds to the current value signal fromcurrent sensor 112 as represented at line 114, as well as to thecorresponding signal from current sensor 122 as represented at line 126.This overcurrent detector may be implemented, for example, as ahigh-speed comparator of a type LM119 marketed by National SemiconductorCorp. (supra). This over-current detector is “hard wired” such that itsresponse is both immediate and reliable in providing a fault signal atline 204 leading to the Timer/Shutdown logic 70 which carries out ashutdown procedure and appropriate indication at display 92.Over-voltage detector 202 responds to voltage values at line 110 asrepresented at line 138 and corresponding voltage values at line 124, asrepresented at line 144. Where that detector 202 determines that themonitored voltage at either line 138 or line 144 is above apredetermined limit, then a corresponding fault signal is directed vialine 206 to the Timer/Shutdown logic 70. The apparatus, as before, isshutdown and an appropriate message is provided at the display 92.Over-voltage detector 202 similarly is “hard wired” in the interest ofprecision and speed and may be provided as a type LM119 comparator asdescribed above.

As indicated earlier herein in connection with FIG. 1, an aspect of thepresent invention is a recognition that a squarewave with positive-goingand negative-going waveform components and which exhibits substantiallyno d.c. term is derived which occurs at a base frequency value (F1) andat a burst repetition frequency value (F2) less than that base frequencyvalue. The electrical characteristics of tissue with which theelectrodes are associated may be analyzed in conjunction with theapplied waveform for diagnostic purposes as well as being used fortherapeutic purposes. For diagnosis, the voltage data and current dataobtained by monitoring can be treated mathematically in a variety offoreseeable approaches. For example, Fourier transforms of theparameters of voltage and current can provide analysis. Additionally,the Laplace equation can be solved in various ways to compute admittanceas a function of space within a tissue sample by applying a changingvoltage at various points across the sample. This is referred to aselectrical impedance tomography. The following Laplace equation relatesthese:∇·σ∇φ=0   (1)The del or ∇ operation is merely a shorthand way to write the sum ofthree partial differentials of an unknown function distributed throughspace, φ being potential and σ being admittance. The form varies withthe coordinate system used. For a Cartesian coordinate system and a realfunction, R, (without complex i components) the following expressionobtains:∇R=∂R/∂x+∂R/∂y+∂R/∂z   (2)A partial differential like ∂R/∂x represents a change in R along the xdirection. The del of R is the simultaneous change in all directions atonce. The resulting function is a collection of values spread acrossspace. This is also is called the gradient of R.

A system for permitting diagnostic analysis as well as for subsequenttherapy is represented in FIGS. 5A and 5B which should be combined aslabeled thereon. The system represented in FIGS. 5A and 5B is oneperforming in conjunction with a controller or central processing unit(C.P.U.) with memory, various interfaces and display. Representedgenerally at 210, this system is seen to perform in conjunction with acontroller (C.P.U.) 212. Controller 212 may interact, as represented bybus 214, with a display represented at block 216. Similarly, thecontroller 212 may interact with a manual interface as represented atbus 218 and block 220. Interface 220 may be the receptor of a variety ofinputs such as the manual input or keyboard type function represented atblock 222 and line 224. Also insertable through the manual interface 220may be any of a broad variety of waveform types and parameters includingthe above-noted F1 and F2 waveform frequencies and related data asrepresented by the dashed block 226 and dashed arrow 228. Where thatwaveform data has been mathematically processed to develop correspondingcoefficients and the like, then such library of processed coefficientscan be introduced at the manual interface 220 as represented at dashedblock 228 and dashed arrow 230. Similarly, biologic history, eitherderived from the patient under investigation or pools of patients, canbe introduced at the manual interface 220 as represented at dashed block232 and dashed arrow 234. In conventional fashion, interactive remotedata can be provided at the controller 212 as represented at a serialinterface 236 and interactive bus 238. The inputting of remote data tothe interface 236 is represented at dashed block 240 and line 242.Correspondingly, serial data can be outputted which, for example, willrelate to diagnostic and therapeutic information as represented at line244 and dashed block 246. Power to the components of the system 210 isrepresented at block 248 and arrow 250.

The microprocessor driven feature of system 210 further lends itself tofacilitating the physician-patient relationship in developing treatmentas well as diagnosis and data collection. In this regard, the controllerand associated memory functions may be operationally associated with apatient carried patient diagnostic card (PDC). Such diagnostic cards maycarry calendar and time information for carrying out therapy sessions aswell as physician elected voltage and current criteria, for example, asdiscussed in connection with FIG. 4A above. Additionally, the cards maycarry the biologic history data as discussed in connection with block232. The cards at hand are memory containing and microprocessor drivenand are referred to generally as “smart cards”. A detailed discourseconcerning the cards may be accessed at: http://www.smartcardbasic.com/.This feature is represented in FIG. 5A in conjunction with block 247which provides for a patient PDC read/write component which isinteractively associated with CPU 212 as represented at bus 249. In itsuse, the patient will insert the card in the patient PDC read/writecomponent 247 as represented at block 251 and arrow 253. Until the cardis so inserted, for example, on the proper day and at the proper timefor therapy, the system 210 will not be enabled. The patient has onlythe option of initiating a procedure, in effect under a prescriptionprovided by a physician and written into the PDC card 251. Dependingupon a prescription, should the patient pick an erroneous day or anerroneous time of day for the therapy, the card may be programmed toblock therapy and record the failure to undergo therapy. At the end of agiven therapy session, CPU 212 will write to the card 251 providing allor select portions of collected data which it may have developed asdiscussed latter herein. The cards may be utilized ultimately in anHIPPA compatible format for a universal records system.

In the event of an improper electrode coupling, channel imbalanceover-currents and the like the system 212 will automatically shut downas described earlier herein.

System 210 may perform in conjunction with one or more channels and anassociated return electrode function. In order to customize waveformparameters or waveshapes (see FIG. 2), the controller 212 suppliesdigital information to a digital-to-analog converter function asrepresented at bus 252 and block 254. The resulting analog output atline 256 is directed to a distribution function similar to a multiplexeras represented at block 258. Block 258, in turn, distributes the analogwaveforms to a select number of channels. In this regard, n (three ormore) channels are shown in the instant representation by eachresponding to an analog input directed from the distribution function258 to channel input lines 260-262. Line 260 is seen directed to theinput of a channel number one driver at block 264, the output of whichis provided at line 266. Line 261 is directed to the input of a driverfor channel two as represented at block 268, the output of driver 268being at line 270. Line 262 extends to the nth driver as represented atblock 272. This nth channel driver provides an output at line 274.

Looking additionally to FIG. 5B, line 266 is seen to extend to a firstchannel load coupler represented at block 276. Coupler 276 functions,for example, to handle varying impedances of an associated electrodewith the biological subject being diagnosed or investigated as well astreated. This impedance-based function may be automated ultimately fromthe controller 212, as initially represented by the control input arrow278 labeled “C₁”. The output of coupler 276 at line 280 provides aselected waveform to a first channel electrode represented at block 282.This electrode 282 for channel one is shown electrically associated, asrepresented at arrow 284, with a biological subject represented at thedashed boundary 286.

The second channel output at line 270 is seen directed to a secondchannel load coupler represented at block 288 having an outputrepresented at arrow 290 extending to the second channel electroderepresented at block 292. Signal coupling of electrode 292 with thebiological subject 286 is represented by an arrow 294. Load coupler 288also is controllable, for example, to carry out automated impedancehandling by control inputs shown at arrow 296 and labeled “C₂”. An nthchannel driver output at line 274 is shown directed to a channel n loadcoupler represented at block 298 having an output represented by arrow300. Arrow 300 is seen directed to the nth electrode represented atblock 302. The electrical association with the electrode 302 and thebiological subject 286 is represented at arrow 304. Control over a loadcoupler n at 298 is provided, for example, for purposes of automatedimpedance handling as represented at arrow 306 which is labeled “C_(n)”.

Returning to FIG. 5A, this load coupler control as represented at lines278, 296 and 306 is carried out by the controller 212 operating inconjunction with a control interface as represented at block 308.Interactive control to the interface 308 is represented at bus 310 andthe arrows 278, 296 and 306 reappear in conjunction with the notedlabels: C₁, C₂, and C_(n).

Returning to FIG. 5B, one or more return electrodes is provided with thesystem 210 as represented at block 312. The electrical associationbetween the return electrode function 312 and the biological subject 286is represented at arrow 314.

System 210 provides for the monitoring of both electrical and biologicalparameters in order to acquire sufficient data for mathematicalprocessing or treatment and additionally to develop safety features.Accordingly, the excitation outputs at lines 280, 290 and 300 aremonitored in addition to a monitoring of the current extant at thereturn electrode 312. A current monitor represented at block 320 andline 322, monitors current values at line 280. An RMS value of monitoredcurrent, i₁, is represented at arrow 324. Similarly, the voltage levelsat line 280 are monitored, as represented at block 326 and line 328, toprovide a monitored RMS voltage output labeled, V₁ at arrow 330. TheseRMS current and RMS voltage values permit the system 210 to carry out asignal power monitoring function. The excitation outputs at line 290 ismonitored for current values as represented at block 332 and line 334.An RMS value of monitored current for this second channel is labeled i₂at arrow 336. An RMS voltage level at excitation output line 290 ismonitored, as represented at block 338 and line 340, to provide amonitored voltage output labeled V₂ at arrow 342. Current monitoring ofthe excitation output at line 300 is provided for the nth channel asrepresented at block 344 and line 346. This develops an nth channelmonitored RMS current signal labeled i_(n) at arrow 348. Similarly,voltage at line 300 is monitored as represented at bock 350 and line 352to provide a monitored RMS voltage output labeled V_(n) at arrow 354.

Biological monitoring of the subject 286 is represented at block 356 anddual arrow 358. The type of monitoring data is elected by the attendingphysician and will include, for example, respiratory rates, bloodoxygen, heart rate, temperature, brain wave data and the like. Theresultant data stream is represented at bus 360. Monitoring function 356also may be utilized in conjunction with select biological parametersfor homeostasis in conjunction with determined biological limits forsuch biological parameters. With this arrangement, trends can bemonitored and warnings supplied from the controller 212 in the event ofadverse reactions during diagnosis or treatment. Finally, current extantat the return electrode 312 is monitored as represented by block 362 andline 364. This monitor provides a return current signal labeled i_(R) atarrow 366.

In general, the thus monitored data will be analog in nature and isintroduced to the controller 212 following its conversion to digitalformat. In this regard, returning to FIG. 5A, the analog monitored RMSvoltage signals V₁, V₂ and V_(n) reappear in conjunction with respectivearrows 330, 342 and 354. Similarly, the monitored RMS current values i₁,i₂, in and i_(R) reappear with respective arrows 324, 336, 348 and 366.Finally, bus arrow 360, carrying biological data, reappears. All ofthese signals are shown being introduced to a signal conditioning andselection function 368 which selectively conveys them, as represented atline 370, to an analog-to-digital converter represented at block 372.Converter 372 samples the data at line 370 and provides a correspondingdigital data input to controller 212 as represented at bus 374.

As noted above, such monitored data also may be written to the patientPDC 251 by CPU 212 either during or at the termination of a giventreatment session. The resultant data can be downloaded to othercomputer facilities for the purpose of building data bases over apatient pool, for individual patient analysis. The data may be employedfor carrying out trending analyses and the like.

As in the earlier embodiment, system 210 employs “hard wired”overcurrent and overvoltage detection components. In this regard, forthe first channel, the monitored current value output, represented atblock 320, is provided at line 404. In similar fashion, the monitoredvoltage value output for the first channel, as represented at block 326,is provided at line 414. For the second channel, the monitored currentvalue output of block 332 is provided to line 405. The monitored voltagevalue output as derived at block 338 is provided at line 415 for thesecond channel. Finally, the monitored current value output deriving atblock 344 for the nth channel is provided at line 406. The correspondingvoltage value output derived at block 350 is provided at line 416.

Monitoring signal carrying lines 404, 405 and 406 representinginstantaneous current values and corresponding respectively with thefirst, second and nth channels to an overcurrent detector represented atblock 408. Upon detection of an overcurrent, as represented at line 410and block 412 seen in FIG. 5A, the hard wired system shutdown feature isimplemented to turn off current to all electrodes. In similar fashionmonitoring signal carrying lines 414, 415 and 416, representinginstantaneous voltage values and corresponding respectively with thefirst, second and nth channels are directed to a hard wired overvoltagedetector represented at block 418. Upon the occurrence of an overvoltagecondition, as represented at line 420 and block 412, a hard wiredovervoltage system shutdown ensues in the manner similar to thatoccurring with overcurrent conditions.

Peal-to-peak voltage and current values also are useful forcomputer-based analytic purposes. Accordingly, peak current atexcitation line 280 is monitored as represented at block 380 and line382. The resultant first channel monitored peak current signal, whichmay be the peak current of a given cycle or an average peak currentmeasured over a number of cycles, is represented at arrow 383 labeled,

_(1p). Peak current is monitored at excitation line 290 for the secondchannel as represented at block 388 and line 390. The resultant secondchannel monitored peak current signal is represented at arrow 391labeled,

_(2p). This peak current signal also may be representative of a singlecycle or an average value determined over multiple cycles. Lastly, peakcurrent at excitation line 300 is monitored as represented at block 396and line 398. The resultant n^(th) channel monitored peak current signalis represented at arrow 399 labeled

_(np). As with the previous two peak current values, the peak currentrepresented at arrow 399 represents either the peak current of a givencycle or an average of the peak current values for multiple cycles.

Peak voltage at excitation line 280 is monitored as represented at block384 and line 386. The resultant first channel monitored peak voltagesignal is represented at arrow 387 labeled, v_(ip). Peak voltage ismonitored at excitation line 290 for the second channel as representedat block 392 and line 394. The resultant second channel monitored peakvoltage signal is represented at arrow 395, labeled, v_(2p). Finally,peak voltage at excitation line 300 is monitored as represented at block400 and line 402. The resultant nth channel monitored peak voltagesignal is represented at arrow 403, labeled v_(np).

Returning to FIG. 5A, the analog peak monitoring signals are seen to bedirected to the signal conditioning and selection function 368. In thisregard labeled peak current arrows 383, 391 and 399 as well as labeledpeak voltage arrows 387, 395 and 403 reappear as being directed to block368. The latter signal conditioning and selection function selectivelyconveys them, as represented at line 370 to analog-to-digital converterrepresented at block 372. Converter 372 samples the data at line 370 andprovides corresponding digital data to controller 212 as represented atbus 374. As before CPU 212 may write the data to the patient PDC 251during or following a given therapy.

An advantage of utilizing a controller-based system 210 resides in thesubstantial flexibility afforded the user in carrying out not onlytherapy, but diagnosis utilizing variations of excitation inputs andtaking advantage of available memory for recording numerical datacorresponding with measured patient electrical characteristics both withrespect to individual patients and with respect to patient pools. FIGS.6A-6G combine to set forth a flowchart of one such program under whichthe controller 212 may operate.

Looking to FIG. 6A, the program is seen to commence at start node 430and, as represented at line 432 and block 434, a conventionalinitialization procedure then is carried out. The program thencontinues, as represented at line 436 and block 438, to provide for theentry of the identification of the patient. At this point, thepractitioner is afforded the opportunity of entering any preexistingpatient data into memory for purpose of establishing records andgenerally enhancing the data base for the patient. Thus, the programcontinues as shown at lines 440-442 to provide for the entry of patientmedical history, as represented at block 444; the entry of patient datafrom test observation and any observation-based diagnosis, asrepresented at block 446; and the entry of measured patient electricalcharacteristics which might be available, as represented at block 448.The program then continues as represented at lines 450-452 to theinstructions at block 454 which provide for the compiling of preliminarywaveshape selection data. That compilation is then displayed asrepresented at line 456 and block 458. The program then continues, asrepresented at lines 460 and 462, to the query posed at block 464. Block464 affords the practitioner an opportunity to determine whether or notto access a library of waveform parameters. Such parameters have beendiscussed, for example, in conjunction with FIG. 5A at blocks 226 and228. In the event such access is desired, then the program continues asrepresented at line 466 and block 468 providing for a display of suchcorrelative stored data. The program then continues as represented atline 470. In the event of negative determination with respect to thequery posed at block 464, then the program continues as represented atline 472 to line 470.

Line 470 reappears in FIG. 6B extending to the query posed at block 474determining whether the practitioner has at this point in time selectedthe waveform parameters desired. In the event that such waveformparameters (waveshape) have been selected, then the program proceeds toinstall that selected waveform as represented at line 476 and block 478.As discussed above, the elected waveform installation also may becarried out by writing to a patient PDC 251 (FIG. 5A).

Where the waveshape has not been selected at this juncture in theprogram, then as represented at line 480 and block 482 a determinationis made as to whether the practitioner wishes to carry out a diagnosticprocedure for purposes of determining an appropriate waveshape. In theevent of a negative determination, then the program reverts to line 470and the query at block 474 as represented by line 484. Where adiagnostic procedure is elected, then as represented at line 486 andblock query 488, a determination is made as to whether a stimulus-baseddiagnostic interrogation is desired. In the event that suchinterrogation is called for, then, as represented at line 490 and block492 a patient electrical parameter diagnosis is called.

Referring to FIG. 7, a generalized version of this subroutine isdepicted in flowchart fashion. The routine commences at block 500providing for a display of the stimuli which are available with thesystem for selection by a practitioner. Then the routine continues asrepresented at line 502 and block 504 wherein the practitioner selects aparticular stimulus, for example, whether it be of a pulse variety, astep variety or a frequency sweep variety. As represented at line 506and block 508 the mode of the selected stimulus is selected. This modemay be a single shot impulse, a continuous excitation or a gatedexcitation. Then, as represented at line 510 and block 512, thepractitioner selects one of the thus displayed modes and the programcontinues as represented at line 514 and block 516. The system providesa prompt for selecting ranges with respect to such parameters asfrequency, pulse repetition frequency, duty cycle and sweep range. Wherea sweep frequency diagnosis is desired, then, as represented at line 518and block 520, that range data is selected and, as represented at line522 and block 524, a diagnostic stimulus is applied to the patient and,as represented at line 526 and block 528, responses are measured andrecorded. Such a response, for example, may be current waveshape at thefeedpoint of the electrodes. Then, as represented at line 530 and block532, certain characteristics of the measured responses are calculatedand recorded. Such characteristics will, for example, be a quotient formof treatment of the Fourier transforms of the applied voltage squarewaveand of the current waveform at feedpoint of the electrodes.Additionally, Laplace based analysis may be carried out. Next, asrepresented at line 534 and block 536 a query is made as to whether theapplication has terminated. In the event that it has not, then theprogram loops, as represented at line 538, and continues the applicationof stimulus. In the event the application of stimulus is terminated,then as represented at line 540 and block 542, the calculatedcharacteristics are displayed and, as represented at line 544 and node546 the routine returns.

Returning to FIG. 6B and block 492, upon the return of the subroutine,as represented at line 548, the program reverts to node A whichreappears at FIG. 6A at line 450 extending to line 452.

Where the system is more dedicated in that it provides diagnosticactivity based upon sweep frequencies then a routine described inconnection with FIG. 8 may be called. Looking to that figure, theroutine commences at node 560 and line 562 leading to block 564. Block564 provides for the display of available sweep frequencies along withappropriate prompts to aid the practitioner in their selection. Then, asrepresented at line 566 and block 568 a query is made as to whether azone or range of sweep frequencies has been selected. In the event thatit has not, then as represented at line 570, the program loops untilsuch time as a selection has been made. Upon making the sweep frequencyselection, then as represented at line 572 and block 574 the routinedisplays available repetition frequencies and duty cycles along with anappropriate selection prompt. Then, as represented at line 576 and block578 a query is made as to whether the selections made available at block574 have been made. In the event they have not, then, as represented atline 580, the routine loops until such selection is made. Where aselection has been made, then, as represented at line 582 and block 584successive increments of the sweep frequency range are applied to thesystem electrodes and, as represented at line 586 and block 588 oneselected pulse repetition frequency and duty cycle is applied for eachsweep increment. The routine then continues as represented at line 590and block 592 wherein, for each sweep increment, the routine acquiresthe drive voltage value and, as represented at line 594 and block 596,for each sweep increment, the routine acquires the load current orcurrent at the electrode feed point. Then, as represented at line 598and block 600, for the instant application, for each sweep increment aFourier coefficient with respect to both voltage and current iscomputed. As noted above, other mathematical processing involvingLaplace equations and the like can be carried out. Then, as representedat line 602 and block 604, accumulated data is displayed from which thepractitioner may form a diagnosis. The routine continues as representedat line 606 and block 608 so as to determine whether or not the sweepfrequency zone has been completed. In the event that is has not, thenthe program loops as represented at lines 610 and 582 until thefrequency sweep has been conducted throughout the elected zone. Wherethat sweep zone has been completed, then as represented at line 612 andnode 614, the routine returns and the program reverts to the earlierdescribed node A.

Returning to FIG. 6B, where the query posed at block 488 results in anegative determination, then as represented at line 620 and block 622, adetermination is made as to whether the waveform selection has beencompleted. In the event that it has not, then the program loops asrepresented at line 624. However, where waveform selection is completed,then as represented at lines 626 and 476, the waveform is installed asearlier described in connection with block 478. As represented at line628 and block 630 the selected waveform parameters are displayed. Thoseparameters will, for example, be the base or higher frequency, the pulserepetition frequency and duty cycle. With such display, the programcontinues as represented at lines 632 and 634.

Line 634 reappears in FIG. 6C. Looking to that figure, the line is seento be directed to block 636 providing for the loading of treatmentintervals. Those intervals will be the total treatment time which willbe a time, for example, representing the maximum allowable time oftreatment accumulated over a lengthy interval such as a month or year.Next, the dosage interval is loaded. The dosage interval is the intervalof a given treatment and the accumulation of dosage intervals cannotexceed the total treatment time These treatment intervals also may bewritten to the patient PDC 251 (FIG. 5A). As represented at line 638 andblock 640, both the elected treatment (DOSAGE, ACCUMULATED) intervalsare displayed and the program continues as represented at line 642 andblock 644 wherein the power source status is.acquired. For example, ifthe power source is a battery, then it is important to know that thebattery has sufficient capacity to power the system for the dosageinterval at hand. Accordingly, as represented at line 646 and block 648an inquiry is made as to whether the power source is ok. In the eventthat it is not, then as represented at line 650 and block 652 theresultant error is displayed to the practitioner and, as represented atline 654 and block 656, the procedure is stopped and the program revertsto line 634 as represented at line 658.

If the power source is determined to be adequate, then as represented atline 660 and block 662, prompts are displayed for the entry ofelectrical parameter limits and ramp rate. The program then continues asrepresented at line 664 and block 666 wherein the ramp rate isinstalled. Next, as represented at line 668 and block 670, the rampcurrent and voltage specifications are entered. Following suchinstallation, as represented at lines 672 and block 674 acceptable rampcurrent and slope ranges are installed. This data has been discussedabove in connection with FIG. 4A. The program continues as representedat line 676 and block 678 wherein the balance window of acceptancebetween channels is entered, or a preprogrammed default interval isaccepted. Next, as represented at line 680 and block 682 prompts aredisplayed for using or applying physiological monitors as have beendiscussed above. The program then continues as represented at line 684.As before, the information represented at blocks 666, 670, 674 and 678may be written to PDC card 251 (FIG. 5A).

Line 684 reappears in FIG. 6D. Looking to that figure, the line is seendirected to block 686 which provides for the displaying of promptsinstructing in the proper placement of the electrodes. Then, asrepresented at line 688 and block 690 the program acquires the startingor baseline monitored physiological data for the patient. It is fromthis baseline data that trends and the like can be evaluated todetermine the physiological reaction to the treatment on the part of thepatient. Then, as represented at line 692 and block 694 the programdisplays that physiological data which is being monitored. The programthen continues as represented at line 696 and block 698 where adetermination is made as to whether a start command has been received.In the event that a start signal has not occurred, then the programloops as represented by lines 700 and 702. Where a more simpleconfiguration of the system is at hand which is used by the patient, thestart command may be provided by the patient following the enablement ofthe system using PDC 251. This essentially is the only control assertedby the patient over the system. However, the system may shut down due toany of a variety of faults or mistakes which are electrically detected.With the presence of the start command, the program proceeds asrepresented at line 704 and block 706 at which a query is posedquestioning whether a preliminary ramp threshold value has been reached.In this regard, during the ramping interval it is desirable to evaluatethe load impedance for purposes as discussed above, i.e., for example,determining whether the electrodes are properly placed. Thus, theimpedance of each channel is checked during the ramping process.Accordingly, when this preliminary threshold is reached, then asrepresented at line 710 and block 712 the impedances for each channelare derived. Then, as represented at line 714 and block 716, the programcommences to evaluate the impedance for each channel. In block 17, afirst channel, designated “R” is checked with respect to impedance. Inthe event that the impedance is improper, then as represented at line718 and block 720 an aural cue is sounded. The error is set forth in adisplay and a prompt is provided advising the practitioner as to propercorrective procedure. The program then proceeds as represented by line722 to node C which reappears with line 724 extending to line 684. Wherethe first channel impedance is appropriate, then as represented at line726 and block 728 the second channel is checked for impedance, heredesignated as the “L” channel. Where that impedance if found to beimproper, then, as represented at line 730 and block 732 the same formof aural cue occurs along with display prompts as described inconnection with block 720, whereupon, as represented at line 734, theprogram reverts to node C as before. Where the second channel impedanceis proper, then as represented at line 736 and block 738 any remainingchannels are checked, the last herein being represented as channel “n”.Block 738 provides for checking the impedance of channels through thelast. In the event any one of those channels is defective in terms ofimpedance, then as represented at line 740 and block 742, an aural cueis sounded and the error is displayed with a prompt. As represented atline 744, the program then reverts to node C.

Where all channels are properly checked for impedance and all areexhibiting appropriate impedance values, then as represented at line 746and block 748, the current values for each channel are acquired. Then,as represented at line 750 and block 752 a check is made as to whetherthe ramp target (threshold) value has been reached. In the event that ithas not, then the program loops as represented at line 754. Where theramp target (threshold) is reached, the program continues as representedat line 756.

Referring to FIG. 6E, line 756 reappears extending to the query posed atblock 758. That query determines whether or not a system shutdown signalhas been received. It may be recalled from FIGS. 5A and 5B that thesystem incorporates an overcurrent detector and an overvoltage detectorwhich are hard wired to develop a rapid shutdown. A system shutdownfeature, in particular, was described at block 412 in FIG. 5A.Accordingly, when such a signal is received, as represented at line 760and block 762 a shutdown error is displayed and, as represented at line764 and node 766 the program is ended abruptly.

In the absence of a system shutdown, the program starts the dosage timeras represented at line 767 and block 768. Then, as represented at line770 and block 772, a subroutine referred to as “run monitor” is called.

Referring to FIG. 9, the run monitor subroutine is revealed. In thefigure, the program commences at the start node 780 and, as representedat line 782 and block 784, the first channel current and voltage isacquired. Then, as represented at line 786 and 788, the second channelcurrent and voltage values are acquired. In general, these values areacquired for all channels of the system through the nth channel. This isrepresented by line 790 and block 792 providing for the acquisition ofthe nth channel current and voltage values. The routine then continuesas represented at line 794 and block 796 which provides for thederivation of the impedances of all channels. Then, as represented atline 798 and block 800 a determination is made as to whether all derivedchannel impedances fall within a window of acceptance. In the event oneor more does not, then as represented at line 802 and block 804, a runmonitor stop status signal is generated and the subroutine exits asrepresented at line 806 and node E.

In the event the channel impedances all fall within the appropriatewindow, then, as represented at line 808 and block 810 the balance ofcurrent between channels is checked and a determination is made as towhether any balance deficit falls outside a pre-selected window. In theevent that any two channels fail to balance in terms of current, then,as represented at lines 812 and 802, the run monitor stop status signalis generated as represented at block 804. Where the channel currentbalance check is passed, then as represented at line 814 and block 816the power source status is acquired. Acquiring this status becomesimportant where a battery power supply is utilized. Next, as representedat line 818 and block 820, the remaining dosage interval is acquired forpurposes of evaluating the reserve of the power source or battery powersupply. Accordingly, as represented at line 822 and block 824 a check ismade of that power source reserve and, in the event it is appropriate tocomplete the dosage interval, as represented at line 826 and node 828the subroutine returns to the main program. Where the power sourcereserve is not sufficient, then as represented at lines 830, 812, 802and block 804, the noted run monitor stop status signal is generated, asrepresented at line 806 and node E.

Returning to FIG. 6E, node E reappears in conjunction with line 832extending to line 834. Line 834 leads to the query posed at block 836determining whether a run monitor stop signal has occurred. In the eventthat it has occurred, then as represented at line 838 and block 840, anaural cue is generated and an informational error signal is displayed.Then, as represented at line 842 and block 844 the elapsed dosage timeis saved in memory and the program continues to node D. Node D reappearsin FIG. 6D at line 702 extending to line 696, which in turn leads toblock 698 where a start command is awaited.

Returning to FIG. 6E, where no run monitor stop status signal has beenreceived, then as represented at line 848 and block 850 a subroutinereferred to as “wavecheck” is called.

Referring to FIG. 10, the wavecheck subroutine is illustrated. In thefigure, the subroutine commences with the start node 860 and line 862leading to block 864. At block 864, instructions are provided for theacquisition of waveform voltage characteristics for the first channel.Those characteristics, in effect, identify the waveform. Next, asrepresented at line 866 and block 868, the corresponding waveformcurrent characteristics for the first channel are acquired. Thesefeedpoint current characteristics, as discussed above, will containinformation or data relating to, inter alia, the impedancecharacteristics of the tissue region through which current is passing.Next, as represented at line 870 and block 872, the waveform voltagecharacteristics for the second channel are acquired. Then, asrepresented at line 874 and block 876 the waveform currentcharacteristics for that second channel are acquired. These activitiescontinue for all channels until the last or nth channel. That lastchannel waveform characteristic acquisition operation is represented atline 878 and block 880. Next, as represented at line 882 and block 884the waveform current characteristics for the nth channel are acquiredand the routine continues as represented at line 886. With the aboveacquisitions, data is available for analyzing the channel associatedwaveshapes. This data as well as any computed analysis as discussedbelow may, for example, be downloaded or written to PDC card 251. Avariety of analyses may be carried out, for example, one analysis mayprovide for the determination of Fourier coefficients for each channel.Accordingly, as represented at block 888 such coefficients are computedfor the first channel. Then, as represented at line 890 and block 892,the second channel Fourier coefficients are computed. Such computationof these coefficients is carried out for all channels in the system. Thelast such channel Fourier coefficient computation is accordinglyrepresented at line 894 and block 896 calling for the computation of thenth channel Fourier coefficients. Inasmuch as it is quite desirable toretain and compile these computed coefficients, the routine thenproceeds as represented at line 898 and block 900 providing for theirrecordation. The program then continues as represented at line 902 andblock 904 to determine whether the computed Fourier coefficients foreach channel fall within a predetermined coefficient window. In theevent they do not, then, as represented at line 906 and block 908 a stopstatus signal is generated and directed as represented by line 910 andnode F. Where the Fourier coefficients all fall within the appropriatewindow, the routine continues as is represented at line 912. At block914 all channels are investigated for the presence of a d.c. term. Wheresuch a d.c. term is present, then as represented by line 916 and block908, a stop status signal is generated. Where no d.c. term is present inany channel, then as represented at line 918 and block 920 the voltagepeaks for each channel are tested against window value. Where one ormore of those voltage peaks is without the window, then as representedat lines 922, 916 and 906 leading to block 908, a stop status signal isgenerated. Where the tests posed at block 920 are met, then asrepresented at line 924 and block 926, the RMS current within eachchannel is tested against a window. Where that test is not met for oneor more channels, then as represented at lines 928, 922, 916 and 906 aswell as block 908, a stop status signal is generated. Where the testsposed at block 926 are met, then as represented at line 930 and node932, the subroutine returns to the main program.

Node F appears in FIG. 6E. Returning to that figure, node F is seenextending to lines 940, 942 and block 944. At the latter block, a testis made as to whether a wavecheck stop status signal has been generated.Where such a signal has been generated, then as represented at line 946and block 948 an aural cue is generated and the wavecheck error isdisplayed. Then, as represented at line 950 and block 952 the elapseddosage time is saved in memory and the program reverts to node D asrepresented at line 954. Node D reappears in FIG. 6D in conjunction withline 702.

Returning to block 944, where a wavecheck stop status signal has notbeen received, then the program proceeds as represented at line 956.

Referring to FIG. 6F, line 956 reappears in conjunction with block 958.This portion of the program is concerned with checking or reviewing theprogress of therapeutic treatment while it is underway. Block 958provides a display with continued treatment prompts describing thereview procedure. Then, as represented by line 960 and block 962 aprogram accesses and displays the waveform characteristics thus farrecorded in the course of the treatment. Then, as represented at line964 and block 966 the program queries as to whether a treatment changehas been indicated as desirable by the practitioner. In the event suchchange has been indicated, then as represented at line 968 and block 970the practitioner is aided by the accessing and display from the memorylibrary of waveform parameters which may be available for such a change.The program then progresses as represented at line 972 and block 974wherein a query is made as to whether a therapy restart has beenrequested. In the event that it has been requested, then as representedat line 976 and block 978 the therapy data which heretofore has beenrecorded is saved and as represented at line 980 the program reverts tonode A which appears at line 550 in FIG. 6A. Where the query posed atblock 974 indicates that no therapy restart is indicated, then theprogram continues as represented at lines 982, 984 and block 978.

Returning to the query posed at block 966, where no treatment change hasbeen indicated by the practitioner, then the program updates the patientphysiological data as represented by line 984 and block 986. Followingthis update, as represented at line 988 and block 990 the updatedphysiological data is displayed and the program continues as representedat line 992 to the query posed at block 994. That query questionswhether the physiological data limit threshold has been reached. In theevent that it has, then as represented at line 996 and block 998 anaural cue is generated and the pertinent physiological data isdisplayed. Then, as represented at line 1000 the program reverts to nodeD which reappears in conjunction with line 702 in FIG. 6D. Where nophysiological data limit threshold has been reached, then the programcontinues as represented at line 1002.

Line 1002 reappears in FIG. 6G extending to block 1004. The query posedat block 1004 determines whether a physiological data limit or trendanalysis has reached a warning threshold. This means that enough changehas been made in the physiology of the patient to merit bringing thatchange to the attention of the practitioner. In the event of a trendthreshold being reached, as is represented at line 1006 and block 1008,an aural cue is generated and the trend data is displayed. The programthen continues as represented at lines 1010 and 1012. Where the queryposed at block 1004 indicates that no warning threshold has beenreached, then, as represented at block 1014, the program queries as towhether an external stop has been received. In the event that such astop has been received, as represented at line 1016 and block 1018 thetherapy data is saved in memory which may include PDC card 251 memory,and the program reverts to node D as represented at line 1020. Node Dreappears in connection with FIG. 6D at line 702.

Where no external stop has been received, then as indicated at line 1022and block 1024 a query is made as to whether the remaining dosage timeis equal to zero. In the event that it is not, then as represented atline 1026 and node G the program loops. Node G reappears in FIG. 6E inconjunction with line 1028 extending to line 770. Where dosage timeremains, then as represented at line 1030 and block 1032 all currentdrives to the electrodes are terminated and the program continues asrepresented at line 1034 and block 1036 which provides for therecordation of treatment ending data. The program then ends asrepresented at line 1038 and node 1040.

FIGS. 11 and 12 offer further demonstration of the flexibility of theinstant system in carrying out diagnostic procedures to the extent ofevoking research data and combining some aspects of that research anddiagnosis in ongoing therapy. The latter approach is illustrated inconnection with FIG. 11. Referring to that figure, a therapeutic anddiagnostic system is represented generally at 1050. In general, system1050 performs under the initial observation that a waveform can beapplied to a load of variable and unknown impedance characteristics in amanner wherein electrical characteristics representing the loadmaterial, for example, the human head, can be evolved and mathematicallyprocessed. System 1050 looks to a procedure wherein a conventionallyutilized Limoge signal, at least in its rectangular wave format,initially is employed. In this regard, the higher frequency, F1, will be167 kHz and the gating frequency will be 100 Hz. However, during thetherapy that may change based upon a variety of diagnostic factorsincluding mathematical processing of the feed point voltage and currentwaveforms.

In the figure, the practitioner is afforded a menu display of signalsand indications which are available as represented at block 1052. Thoseavailable signals are derived from a signal library and treatmentinitiation function represented at block 1054 as represented at arrow1056. Manual control for review and treatment selection is provided asrepresented at block 1058 and its association with display 1052 isrepresented at dual arrow 1060. Access to the library and for providingtreatment initiation at block 1054 from the manual review function 1058is represented at dual arrow 1062. Following practitioner review, thewaveform (waveform parameters) is selected and, as represented at arrow1064, a “prescription” is provided as represented at block 1066 which,as represented at arrow 1068 instructs the treatment initiation functionat block 1054 as to the election of a particular waveform and treatmentduration. At the commencement of a procedure, a more or less standardwaveform as above described typically will be elected. Accordingly,treatment initiation at block 1054 provides for the enablement of a wavegenerator at the noted higher frequency, F1, as represented at bock 1070and arrow 1072. Simultaneously, enablement is provided as represented byarrow 1074 to a gating function represented at block 1076 providing fora pulse repetition frequency (PRF) and duty cycle and presented at thefrequency, F2. The output of wave generator 1070 and the gating outputfrom control 1076 are provided, respectively, as represented by arrows1078 and 1080 to a gated wave generator represented at block 1082. Theresultant rectangular wave waveform output then is present at arrow 1084which is seen to be introduced to a load coupler represented at block1086. Load coupler 1086 is associated with the patient or biologicspecimen represented at block 1088 through electrodes as earlierdescribed and this association is represented by input arrow 1090 whichis electrically operatively associated with a current sensing functionrepresented at block 1092. The continuation of the output to electricalcoupling with the patient 1080 is further represented at arrow 1094. Anelectrical return is represented in general by arrow 1096. Load coupler1086 incorporates components functioning to optimize the coupling of thesignal at arrow 1084 with the load represented at block 1080. Typically,this coupler function is implemented with a form of filter or LC networkwhich can be automated in terms of handling the driving point sourceimpedance at arrow 1084 in relation to the varying input impedances ofthe specimen 1080. Such coupler function 1086 may not be required in theevent that the load impedance at hand is low enough and if the reactivecomponent of the load is insignificant.

As described in connection with FIG. 1, the system 1050 is concernedwith the difference between the waveform of the driving voltage and theresulting current waveform evoked as a consequence of current passingthrough the biologic specimen 1080. The squarewave drive voltage atarrow 1084 is tapped as represented at arrow 1098 and directed to adrive voltage signal conditioning function represented at block 1100.Similarly, the current proportional signal derived from the currentsensor 1092 is tapped as represented at arrow 1102 which is directed toa load current signal conditioner represented at block 1104. Eachwaveform defining signal as represented at blocks 1100 and 1104 isdirected, as represented by respective arrows 1106 and 1108 to aprocessing function represented at block 1110. For the presentembodiment, that processing function includes the deriving of Fouriercoefficients, such coefficients representing a mathematical descriptionof the electrical form of waves, typically assigning amplitude and phaserelationship with respect to frequency components of a wave. For thepresent embodiment, the processing involved develops Fourier coefficientdifferences, the amount of such a difference being related to theimpedance characteristics at the specimen 1080. These difference valuesare sometimes referred to as differential coefficients. The data, now indigital form, derived at block 1110 is directed, as represented at arrow1112 to a correlator function represented at block 1114. Thiscorrelation function receives the processed coefficient data asrepresented at arrow 1112 as well as data from a library ofmathematically processed coefficients represented at 1116 and arrow1118. Library function 1116 represents data from a population ofpatients correlating coefficient differences, for example, with syndromerecords of that patient population.

The correlation can, for example, utilizing techniques of artificialintelligence and the like evolve a diagnosis as to the physical statusof the patient 1080. That diagnosis is represented at arrow 1120 andblock 1122. The resultant diagnosis is provided, along withcorresponding signal data to the signal library function at block 1054as represented by the dashed arrow 1124.

Additionally, as represented at arrow 1126 and block 1128 from theFourier coefficients, a therapeutic waveshape can be identified andultimately reconstructed. That data is presented as represented at arrow1130 to a nomination of signals for treatment function, in effect,constructing the frequency F1, F2, durations. That function isrepresented at block 1132 which also responds to treatment initiationenablement ultimately developed from the manual selection function 1058and represented as being asserted via arrow 1134. The output of thenomination function 1132 is represented at arrow 1136 and prescriptionblock 1138, the data from which is asserted to the treatment initiationfunction 1054 as represented at arrow 1140.

The system of the invention can be utilized with a variety of electricalstimuli applied to the patient through the electrodes which, in turn,may be varied to evolve a diagnostic form of data. In this regard, thediagnostic stimulus is applied; responses are measured and recorded; andcharacteristics are calculated and recorded. FIG. 12 looks to a sweepfrequency implementation of this diagnostic approach. Looking to thefigure, the system is revealed in general at 1150 to be implemented withan interrogation program represented at block 1152. The underlying tenetof the waveform utilized resides in the requirement that no deleteriousd.c. term be present in the waveform applied. The interrogation program1152 carries out a sweep of frequencies in a predetermined zone offrequencies at the earlier-noted higher frequency, F1. The program alsomay sweep within a zone of gating frequencies, F2. Further, theamplitudes of the positive-going and negative-going components of thewaveforms developed in this sweep function, may be adjusted within theconfines of the zero d.c. term criterion. Interrogation program 1152provides a control to a wave generator at the higher, F1, frequency asrepresented at arrow 1154 and block 1156. Similarly, an interrogationcontrol is asserted to a gating wave PRF and duty cycle correspondingwith frequency F2 as represented at block 1158 and arrow 1160. Theresultant output of generator 1156 is asserted, as represented at arrow1162, to a gated wave generator function represented at block 1164. Thegating feature of that generator function 1164 is provided from block1158 as represented at arrow 1166. In carrying out a sweep frequencyanalysis, waveshapes for a sequence within a range defined betweenstarting and ending frequencies would be asserted in timed sequentialfashion to generator 1164 in combination with corresponding gating wavedata as represented at arrow 1166. Additionally, the frequency assertedfrom arrow 1162 can be stabilized and the gating data from arrow 1166can be swept in a range or zone extant between beginning and endinggating data signals.

As before, the rectangular wave output from the generator function atblock 1164 is asserted as represented at arrow 1168. The sweep frequencyrange of application generally will be provided as zones which will fallwithin boundaries of about 100 kHz up to about 10 mHz, while the burstfrequencies, F2 generally will fall within ranges which are, in turn,within bounds of about 10 Hz to one kHz. These sweep signals asserted atarrow 1168, as before, are introduced to a load coupler functionrepresented at block 1170. Coupler 1170 has the function described abovein connection with block 1086. The drive output from coupler 1170 isrepresented at arrow 1172 through the current sensing functionrepresented at block 1174 and then, as represented at arrow 1176 andblock 1178 through an electrode to the biologic specimen or patient. Thereturn from the corresponding electrode at the patient 1178 isrepresented in general by the arrow 1180.

As before, the rectangular wave evolved voltage waveform at arrow 1168is tapped as represented at arrow 1182 and signal conditioned asrepresented at block 1184 to provide a scaled signal corresponding withthe drive voltage waveform as represented at arrow 1186. The output ofthe current sensor 1174 is directed as represented at arrow 1188 to aload current signal treatment component represented at block 1190 toprovide a corresponding waveform defining output represented at arrow1192. As before, that output and the output at arrow 1186 are processedas represented at block 1193 to provide corresponding Fouriercoefficients. Digital data representing those coefficients is submitted,as represented by arrow 1194, to a correlator function represented atblock 1196. Note, that for system 1150, the correlator function 1196 isreceiving sweep frequency data for compilation and analysis. Generally,from that data, the correlator function 1196 looks for anomalies in thefrequency-response energy transfer characteristics of the biologicspecimen or patient 1178. As before, by reference to the drivingrectangular wave characterized voltage waveform difference ordifferential data can be evolved. Resistive impedance characteristics aswell as reactive impedance characteristics of the analyzed specimen at1178 are available with the system. This body of data for each patientis submitted to memory for the purpose of evolving an associateddatabase carrying patient data and the noted wave coefficients andprocessed coefficients. This database is represented generally at 1198and for illustrative purposes is represented by “Patient Data 1” block1200; “Patient Data 2” block 1201 and that patient data collection willcontinue until an nth or last inserted “Patient Data” collectionrepresented in block 1202 as patient data n. The outputs from block1200-1202 are shown respectively at 1204-1206 being directed to thecorrelator function 1196. Function 1196, as represented at arrow 1208and dashed block 1210 may employ coefficient input from arrow 1194 aswell as data from the database 1198 to carry out a predictive diagnosisfor comparison with other tests. Such diagnoses predict that other testsmay well verify the condition predicted by the correlator function 1196.On the other hand, an enhanced diagnosis in time and scope may bedeveloped wherein, due to substantial database experience evolved fromthe data extent of the database 1198, a diagnosis of high probabilitycan be outputted. Such data base management procedures as involveartificial intelligence and/or neural networking may be employed toachieve this enhanced diagnostic procedure.

Since certain changes may be made in the above-described apparatus,system and method without departing from the scope of the inventionherein involved, it is intended that all matter contained in thedescription thereof or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

1. A system for applying electrical current to an animal having spacedapart first and second surface regions spanning a tissue volumeexhibiting biologically-based electrical impedance, comprising: a firstelectrode assembly positionable for electrical communication at saidfirst said surface region; a second electrode assembly positionable forelectrical communication at said second said surface region; anelectrical generation assembly electrically coupled with said first andsecond electrode assemblies, responsive to a generator input to providean excitation output across said first and second electrode assembliesat frequencies and with waveshapes exhibiting electrical characteristicsvariable in correspondence with said generator input, suchcharacteristics being selectively inclusive of a predetermined basefrequency value and a burst repetition frequency value less than thebase frequency value, a predetermined waveform and predeterminedapplication interval; a current sensor assembly responsive to saidexcitation output for providing a monitored current value output; avoltage sensor assembly responsive to said excitation output forproviding a monitored voltage value output; a controller having aninput, a memory and a display, responsive to values of voltage, currentand frequency provided at said input to derive a corresponding saidgenerator input, responsive to a feed point impedance value provided atsaid input, to said monitored current value output and to said monitoredvoltage value output for deriving an impedance fault signal when saidmonitored current value output and said monitored voltage value outputrepresent an impedance not corresponding with said feed point impedancevalue, responsive to said impedance fault signal to terminate saidgenerator input and to provide perceptible fault information at saiddisplay, responsive to said monitored voltage value output and to saidmonitored current value output to derive digital form data correspondingwith said electrical characteristics and responsive to retain saiddigital form data in said memory.
 2. The system of claim 1 in which saidcontroller is responsive to said monitored current value output toderive a corresponding load current Fourier transform, is responsive tosaid monitored voltage value output to derive a corresponding inputFourier transform, and is responsive to retain said load current andinput Fourier transforms in said memory.
 3. The system of claim 2 inwhich said controller is responsive to mathematically derive the valueof a quotient of said current and input Fourier transforms.
 4. Thesystem of claim 1 in which said controller is responsive to sweepfrequency limit data asserted at said input to derive a said generatorinput providing a sequence of said excitation outputs exhibitingfrequencies extending between said limit data.
 5. The system of claim 4in which said controller is responsive for each frequency of saidsequence of excitation outputs, to said monitored current value outputto derive a corresponding load current Fourier transform, and to saidmonitored voltage value output to derive a corresponding input Fouriertransform and is responsive to retain said load current and inputFourier transforms in said memory.
 6. The system of claim 4 in whichsaid controller is responsive to derive a said generator input providingsaid sequence of excitation outputs wherein a waveshape is created foreach said frequency which is biphasic and exhibits no d.c. term.